Abstract
Size-selective fishing, environmental changes and reproductive strategies are expected to affect life-history traits such as the individual growth rate. The relative contribution of these factors is not clear, particularly whether size-selective fishing can have a substantial impact on the genetics and hence on the evolution of individual growth rates in wild populations. We analysed a 25-year monitoring survey of an isolated population of the Alpine whitefish Coregonus palaea. We determined the selection differentials on growth rate, the actual change of growth rate over time and indicators of reproductive strategies that may potentially change over time. The selection differential can be reliably estimated in our study population because almost all the fish are harvested within their first years of life, i.e. few fish escape fishing mortality. We found a marked decline in average adult growth rate over the 25 years and a significant selection differential for adult growth, but no evidence for any linear change in reproductive strategies over time. Assuming that the heritability of growth in this whitefish corresponds to what was found in other salmonids, about a third of the observed decline in growth rate would be linked to fishery-induced evolution. Size-selective fishing seems to affect substantially the genetics of individual growth in our study population.
Highlights
Human activities have caused phenotypic changes in many ecosystems (Palumbi 2001; Smith and Bernatchez 2008)
For instance, significant shifts in life-history traits have been described. These shifts include maturation at smaller age or size (Heino et al 2002; Grift et al 2003), elevated reproductive effort (Yoneda and Wright 2004) and changes in individual growth rate (Handford et al 1977; Ricker 1981; Thomas and Eckmann 2007). Many of these phenotypic changes may be linked to fisheryinduced evolution
We studied a salmonid population that has been monitored for 25 years
Summary
Human activities have caused phenotypic changes in many ecosystems (Palumbi 2001; Smith and Bernatchez 2008). For instance, significant shifts in life-history traits have been described These shifts include maturation at smaller age or size (Heino et al 2002; Grift et al 2003), elevated reproductive effort (Yoneda and Wright 2004) and changes in individual growth rate (Handford et al 1977; Ricker 1981; Thomas and Eckmann 2007). Many of these phenotypic changes may be linked to fisheryinduced evolution. See Jorgensen et al (2007) for a review on phenotypic traits for which evolutionary changes are likely, and Hard et al (2008) for a discussion of evolutionary consequences of fishing on salmon
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